A novel dual-band circularly polarized (CP) antenna with wide axial ratio (AR) and impedance bandwidths is proposed. Based on a rectangular ground, the antenna consists of a trapezoid patch, an L-shaped strip, a cavity, and T-shaped and L-shaped perturbations. By embedding a feeding line with a trapezoid patch and an L-shaped strip, dual-band input impedance performance and a CP performance at upper band are obtained. In order to achieve a CP performance at the lower band, a T-shaped perturbation is embedded inside the slot. Moreover, the CP performance is enhanced by inserting an L-shaped perturbation at the right bottom corner of the slot. Furthermore, using a cavity underneath the antenna, unidirectional radiation patterns with greatly gain enhancement are obtained. The measured results show that the impedance bandwidths for S₁₁<-10 dB are 22.7% (2.34-2.94 GHz) and 79.8% (4.64-10.8 GHz) while the axial ratio bandwidths (AR<3 dB) are 26.4% (2.3-3 GHz) and 12.6% (5.2-5.9 GHz) at the lower and upper bands, respectively. Additionally, the measured gain is more than 7.4 dB and 2.4 dB in the two operating bands, respectively. Thus, the antenna can be well applied for both 2.4/5.8 GHz WLAN bands and 2.5/5.5 GHz WiMAX bands.

In this paper two novel antennas, suitable for access and backhaul links, are designed, fabricated and tested for a Relay Station in a WiMAX wireless network. A single modified E-shaped patch antenna is described, presenting 10 dB gain over 12.4% bandwidth. This antenna element is used for the design of a 4×4 planar array which provides experimental gain of 21.2 dB. The antenna system on the Relay Station operates at 3.4 GHz and includes one single antenna element for access link realization and an antenna array for the backhaul link realization. These antennas are installed in two configuration arrangements and tested in terms of their radiation performances and coupling effects. The simulated and measured results are quite satisfactory and in good agreement at which the maximum coupling between the access and backhaul antennas is found below -25 dB for all tested cases.

A planar monopole loaded with composite right/left-handed transmission line (CRLH-TL) for broadband LTE mobile phone is presented. The CRLH-TL with a propagation constant of zero is added to widen the input impedance bandwidth of the antenna. The proposed antenna covers the LTE700/2500/GSM850/900/1800/1900/UMTS2100 and WLAN2400 bands. Impedance bandwidths of VSWR<2.5 (S₁₁<-7 dB) ranging from 675 to 1010 MHz and 1690 to 2550 MHz are obtained. The size of the monopole is 60×16×1mm³ which is smaller than most of the LTE antennas. Detailed design considerations of the monopole are described. A prototype is fabricated and tested. Both simulated and experimental results are discussed.

A novel (2×2) high gain circularly polarized rectangular dielectric resonator antenna array integrated with helical-like exciter is proposed. The array offers a maximum gain of 12.9 dBi at the operating frequency. The circular polarization is obtained by incorporating helical-like exciter in the array structure. A prototype of the proposed configuration integrated with helical-like exciter has been fabricated and tested, and the idea has been verified. A good agreement has been obtained between the measured and simulated results.

Radio refractivity values obtained for different heights (Ground surface, 50 m, 100 m and 150 m) over a tropical station, Akure, South-Western Nigeria using in-situ data over a period of five years has been investigated for chaos. Several chaos quantifiers such as entropy, Lyapunov exponent, recurrence plot were used. Determinism was detected in the time series studied at all the levels. Results obtained from the computation of radio refractivity show that the value of radio refractivity decreases with increasing altitude while chaotic quantifiers obtained at ground level and height 100m are found to be more chaotic than the other two levels (50 m and 150 m).

A novel approach to design microstrip ultra-wideband (UWB) bandpass filter (BPF) using modified genetic algorithm (MGA) is proposed in this paper. To achieve high efficiency and accuracy, conventional GA is modified. By improving the fitness evaluation, selection, crossover, and mutation, the two possible drawbacks of conventional GA, i.e., slow rate of convergence and local-best solution, are overcome. The modified genetic algorithm is then applied to simultaneously search for the appropriate circuit topology and the corresponding electrical parameters with UWB characteristic. To demonstrate the effectiveness of the novel approach, a new microstrip UWB BPF is designed and fabricated. Measurement results agree well with the design index and full-wave EM simulated results.

A miniature platform tolerant antenna is presented which is suitable for low frequency applications. A Split Ring Resonator (SRR) antenna loaded with lumped capacitances is proposed. The antenna is compact, low profile and easy to fabricate. It has a maximum dimension of λ/9 and -10 dB bandwidth of 1%. Miniaturized artificial magnetic conductor surfaces (AMCs) are designed using capacitance loaded metal patches with individual elements measuring just λ/70. Placing the SRR above the AMC improves the bandwidth to between 1.5 and 3.5% dependent on the overall size of the AMC and produces a platform tolerant antenna measuring 0.11λ×0.17λ×0.019λ. The performance of the antenna over an AMC with and without vias is studied and discussed. The AMC mounted antenna's performance in free space and over a ground plane is also compared.

In this paper, a miniaturized dual-band bandpass filter with high selectivity and band-to-band isolation is presented. The filter consists of two quarter-wavelength stepped impedance resonators (SIRs) which share a common grounded via-hole and two symmetrical half-wavelength SIRs which are embedded into the inner space to reduce the size of the filter. Two independent mixed coupling paths which are created by the coupling between these SIRs introduce two different passbands. Five transmission zeros (TZs) are generated near the two passbands to achieve high frequency selectivity and band-to-band isolation. To validate the design theory, a dual-band filter operating at 2.45 and 5.2 GHz was designed and fabricated. The size of the proposed filter only occupies 0.095λ_g × 0.109λ_g and the measured 3 dB fractional bandwidth (FBW) of the first and second passbands is 11.5% and 7.4% respectively. The measured results are in good agreement with the simulated results.

In this article, in a simple way, simple relations are derived between the electric field components of an electrically uniaxial medium and those of an isotropic medium. The permittivity of the isotropic medium is the same as the permittivity of the uniaxial medium that is common to the axes transverse to the optic axis. Using the spectral representation, the vector wave equation for the electric field intensity vector of the uniaxial medium is solved for the x directed, y directed and z directed point sources. For the x directed and y directed point sources, the electric field components transverse to the optic axis are written in terms of the corresponding components of the isotropic medium plus some other terms. Part of these terms are closed forms expressions, and the rest are Sommerfeld type integrals. Elements of each group are related to each other by coordinate transformations. The electric field components parallel to the optic axis are shown to be obtained from the isotropic medium components using coordinate transformations. The relations between the uniaxial medium and isotropic medium field components are verified by comparing the results of a previous study in the literature to the results obtained using the relations in this study. Good agreement is achieved between these results.

In this paper, a microstrip double-layered reflectarray element is studied. The unit element consists of a circular patch sandwiched between two substrates and a cross-slotted circular patch placed on the top-most surface. The radii of the two circular patches as well as the cross-slot lengths are varied simultaneously for controlling the phase range and the gradient of the reflection phase angle. Study shows that the sensitivity of the reflection phase angle can be made slower by utilizing substrates with lower dielectric constants. The component performance is studied using a rectangular waveguide and good agreement is found between thesimulation and experiment. A wide reflection phase range of 681.82° with loss magnitude of less than -1 dB is achievable in the reflection phase angle. A complete parametric analysis has been conducted to study the reflection characteristics of the proposed reflectarray unit element.

A new defected ground structure (DGS) with tunable working frequency and reconfigurable bandwidth is proposed in this paper. The prototype combines the conventional DGS with T-shaped patch featuring narrow bandwidth and two such units located symmetrically featuring wide bandwidth. The proposed structure is designed, simulated and measured. By embedding two reversely-set PIN diodes and four varactors, the proposed structure achieves a narrow bandwidth with a tuning range of 21.1% and a wide bandwidth with a tuning range of 24.6%. In comparison, the bandwidth (-10 dB) is about 13.6% for the narrowband state and 49.2% for the broadband state, where an approximately 4-times extension is obtained.

In [1], Hacivelioglu and co-authors criticize my paper, named ``Fringe waves in an impedance half-plane" [2]. Unfortunately, the general scenario of the criticisms is based on misconceptions and lack of basic knowledge in the diffraction theory. Below we give our detailed rebuttals on their comments.

This paper (i.e., [1]) extends PTD to an impedance half-plane problem.

A passive DC magnetic concentrator is designed with transformation optics (TO) and realized by meta-materials. The passive DC magnetic concentrator, based on space compression transformation, can greatly enhance the magnetic field in a free space region, which can be used for e.g. improving the sensitivity of magnetic sensors and increasing the efficiency of wireless energy transmission. The magnetic property of the medium obtained by TO is extremely anisotropic. To solve this, we use magnetic meta-materials made of alternated high-permeability ferromagnetic (HPF) materials and high-temperature superconductor (HTS) materials. We optimize our structure by conducting simulations using the finite element method (FEM), and experimentally demonstrate a strong, 4.74-time enhancement of the DC magnetic field by our meta-material magnetic concentrator. We also demonstrate that a simplified structure with only HPF materials working at room temperature could still give 3.84-time enhancement of the DC magnetic field. The experimental results are in good agreement with the numerical simulations based on FEM.

High-Q inductors are realized on a 3-8 Ω•cm silicon substrate in the buildup of BCB/Cu. Anisotropic wet etching is utilized to remove the silicon in the cavities underneath the spirals from the backside. Examples of 3.5-turn spiral inductors with and without cavity are compared, and their parameter extractions are accomplished with an equivalent circuit model. Compared to the inductor without cavity, the measured peak quality factor of a 8.19-nH inductor with cavity increases from 24 at 0.8 GHz to 39 at 2.5 GHz by 67%, and the inductor with cavity has a wider bandwidth using the same equivalent model. The inductors utilizing this technique have a potential wide application in hand-held RF modules either as part of an off-chip device or as an integrated passive in a silicon interposer.

A novel 180˚ out-of-phase power divider based on stepped-impedance slotline is presented in this article. This power divider employs one T-junction formed by microstrip line and slotline to obtain two out-of-phase dividing signals. Stepped-impedance slotline and lumped resistor are introduced to improve the isolation between output ports. The experimental data show that the proposed power divider has good performance on insertion loss, return losses, isolation, phase balance, as well as group delay over the wide band 5 GHz-10 GHz.

In this paper, a compact tri-band bandpass filter (BPF) using multi-stub-loaded resonator with controllable frequencies is presented. The multi-stub-loaded resonator consists of a main transmission line, two open stubs and a short stub. Characterized by using even- and odd-mode analysis, it is found that the resonator consists three modes, and the modes can be controlled individually, which enables convenient designs of tri-band BPFs. To demonstrate the proposed idea, a tri-band BPF with operating frequencies of 2.45, 3.8 and 5.15 GHz is implemented. Five transmission zeros are generated near the passband edges, resulting in high skirt selectivity. The total size of the filter is 0.19λ_g × 0.13λ_g, featuring compact size. The comparisons of the measured and simulated results are presented to validate the theoretical predications.

Excitation of electrostatic ion cyclotron waves (EICW) in a magnetized dusty plasma by an ion beam is studied taking into account the effect of dust particle size, dust particle charge and dust particle number density variations. The presence of dust grain charge fluctuations modifies the dispersion relation for ion cyclotron waves in dusty plasma. It is shown that in the absence of ion beam, the ion cyclotron mode damps due to dust charge fluctuations and an additional damping dust charge fluctuation mode is induced in plasma. The ion beam propagating parallel to the magnetic field drives ion cyclotron waves to instability via Cerenkov interaction. Using the analytical and numerical results the influence of the relative density of negatively charged dust particles on growth rate of ion cyclotron waves is studied. The dust grain size distribution has also significant contributions on the growth rate of ion cyclotron waves.

A new approach to classify synthetic aperture radar (SAR) targets is presented based on high range resolution (HRR) profiles time-frequency matrix non-negative sparse coding (NNSC). Firstly, SAR target images have been converted into HRR profiles. And the non-negative time-frequency matrix for each of the profiles is obtained by using an adaptive Gaussian representation (AGR). Secondly, NNSC is applied to learn target time-frequency basis of the training set. Feature vectors are constructed by projecting each HRR profile time-frequency matrix to low dimensional time-frequency basis space. Finally, the target classification decision is found with support vector machine and nearest neighbor algorithm respectively. To demonstrate the performance of the proposed approach, experiments are performed with Moving and Stationary Target Acquisition and Recognition (MSTAR) public release SAR database. The experimental results support the effectiveness of the proposed technique for SAR target classification.

A model of solar cell embedding quantum dots in the intrinsic layer of a p-i-n solar cell has been presented. With proper selection of material, size and fractional volume, quantum dots can provide an intermediate band between the valence and conduction bands of the matrix material, which will absorb photons with energy lower than the original bandgap to absorb more incident photons in the otherwise unused spectral irradiance. The design approach to acquire the highest efficiency of the conventional p-i-n solar cell is presented as a benchmark. Quantum dots are then embedded in the intrinsic region of the reference solar cell to improve its efficiency. InAs is chosen to implement the quantum dots, to be embedded in the p-i-n solar cell made of GaAs. With a more packed arrangement of QD's from that in the literatures, the simulation results shows that the efficiency of the conventional GaAs p-i-n solar cell can be increased by 1.05%.